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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-1159) Case style anonymous functions not supported by Scala API
Date Fri, 01 Apr 2016 18:10:25 GMT

    [ https://issues.apache.org/jira/browse/FLINK-1159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15222081#comment-15222081
] 

ASF GitHub Bot commented on FLINK-1159:
---------------------------------------

Github user StephanEwen commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1704#discussion_r58244518
  
    --- Diff: flink-scala/src/main/scala/org/apache/flink/api/scala/extensions/impl/acceptPartialFunctions/OnDataSet.scala
---
    @@ -0,0 +1,111 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.flink.api.scala.extensions.impl.acceptPartialFunctions
    +
    +import org.apache.flink.api.common.typeinfo.TypeInformation
    +import org.apache.flink.api.scala.{DataSet, GroupedDataSet}
    +
    +import scala.reflect.ClassTag
    +
    +/**
    +  * Wraps a data set, allowing to use anonymous partial functions to
    +  * perform extraction of items in a tuple, case class instance or collection
    +  *
    +  * @param ds The wrapped data set
    +  * @tparam T The type of the data set items, for which the type information must be
known
    +  */
    +class OnDataSet[T: TypeInformation](ds: DataSet[T]) {
    --- End diff --
    
    I think you do not need the `TypeInformation` context bound here. Functions should never
need the implicit type info for the input (that is contained in the DataSet already), only
ever for the return type.


> Case style anonymous functions not supported by Scala API
> ---------------------------------------------------------
>
>                 Key: FLINK-1159
>                 URL: https://issues.apache.org/jira/browse/FLINK-1159
>             Project: Flink
>          Issue Type: Bug
>          Components: Scala API
>            Reporter: Till Rohrmann
>            Assignee: Stefano Baghino
>
> In Scala it is very common to define anonymous functions of the following form
> {code}
> {
> case foo: Bar => foobar(foo)
> case _ => throw new RuntimeException()
> }
> {code}
> These case style anonymous functions are not supported yet by the Scala API. Thus, one
has to write redundant code to name the function parameter.
> What works is the following pattern, but it is not intuitive for someone coming from
Scala:
> {code}
> dataset.map{
>   _ match{
>     case foo:Bar => ...
>   }
> }
> {code}



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